There are so many moving parts involved in vacation rentals....more people, in and out of your property every week or few days...people on vacation like to party more, so drinking and running around doing dumb stuff.

You can also push back closing if all parties agree to that. 

[In my scenario below, I was thinking about a share of the equity upon refi (what @Jack Pasmore called "the kicker" or share of the upside) since I don't think the seller would agree the property values at only $450K, even though that's what the rent and NOI say]@Jeremy Dugan In my experience, such a "kicker" is only present when the other party is an "investor" rather than the "lender".

I have house hacked and it was awesome for the most part. I

Its not hard to start , its getting to the finish line is the difficult part . I

Entity Formation & Legal CostsExpenseLow Estimate ($)High Estimate ($)NotesSPV Formation (LLC or LP)$300$1,500Delaware LLC (~$300), legal service fees varyOperating Agreement$500$2,500Template (~$500) or custom legal workPrivate Placement Memorandum (PPM)$2,500$15,000Off-the-shelf ($2,500) vs. custom legalSecurities Filings (Reg D 506(b) or 506(c))$500$2,500SEC & state Blue Sky filingsAccredited Investor Verification (506(c))$1,500$3,000Performed by third-party verification servicesSubtotal: $5,300 – $24,500

The best part is there is no hidden fees.Another thing I love is the bookkeeping and analytics—it keeps everything organized for tax time and helps track cash flow without spreadsheets.

To answer your question directly- you might explore some third party software- brightinvestor is a great platform for this type of data. 

I completed a cost segregation, so at least that part is done.

I suggest setting up a partnership agreement that outlines the financial contributions that each party will make and the distributions each partner will receive.